Brush holder for dynamoelectric machines



May 27, 1958 H. A. GILLIE I BRUSH HOLDER FOR DYNAMOELECTRIC MACHINESFiled Oct. 12, 1956 [Mn/@2760)". Harman A G/W/e; WW ,7, w

H/Ls Attorney United States Patnt BRUSH HOLDER FGR DYNAMOELECTRICMACHINES Harmon A. Gillie, fichenectady, N. Y., assignor to Gen eralElectric Company, a corporation of New York Application October 12,1956, Serial No. 615,721

3 Claims. (Cl. 310-246) The invention described herein relates todynamoelectric machines and more particularly to an improved brushholder of the type utilizing a coiled spring designed for applying aconstant predetermined pressure on a carbon brush regardless of thestate of brush wear.

The brush holders currently used with large dynamoelectric machines areof the torsion spring type wherein a free end or arm of the spring isengageable with a lever arm arranged for applying pressure to the brushduring machine operation. In order to maintain constant pressure whilecompensating for brush wear, the free arm of the spring is progressivelymoved into notches provided on the lever arm body. Thus, as wearincreases, the spring is wound in incremental amounts and thereforecompensates for the greater distance the lever arm must act through toprovide the necessary pressure for urging the brush face into contactwith the commutator.

The principal disadvantage of the above-described structure is that theapplication of a constant pressure on the brush throughout its life isnot obtainable. As a result, pressures less than optimum values maycause uneven brush wear and produce chattering and sparking at thecommutator while pressures too great, accelerate wear of the brush atunreasonable rates. The problem of maintenance posed by the constructionis evident since continual verification must be made of brush pressuresto keep them within acceptable limits. Further, an excessive number ofparts of various sizes and shapes are required in the prior constructionand since diiferent size brush holders are used for various machines, anunusually large inventory of individual parts must constantly bemaintained in stock.

Therefore, an object'of the present invention is to provide a brushholder capable of eliminating the abovedescribed deficiencies whilefurther permitting safe and speedy replacement of a brush withoutresorting to the use of tools or removing any parts from the brushholder assembly.

In carrying out the object of my invention, I have designed the brushholder in the shape of a substantially rectangular box provided withopen ends and having a plurality of spaced parallel channels therein. Abrush is inserted through the top open end into one of the channels andprotrudes at the opposite open end in a direction for contacting thecommutator of the machine. A pair of channels are incorporated in thebox on opposite sides of the brush channel and are of a size to acceptarms of an assembly supporting a constant pressure spring arranged forpressing the brush into firm contact with the commutator. The remainingchannel is utilized for securing the brush holder to a supporting yokeadapted for positioning on a frame of the machine.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which I regard as myinvention, it is believed the invention will be better understood fromthe following description taken in connection with the accompanyingdrawing in which:

Patented May 27, 1958 Figure l is a view in elevation, with parts brokenaway to show details of the brush holder body;

Figure 2 is an end view of the brush holder shown in Figure 1;

Figure 3 is a top view; and

Figure 4 illustrates a constant pressure spring designed for coactionwith the brush holder for urging the brush into contact with acommutator.

Referring now to the drawing wherein like reference characters designatelike or corresponding parts throughout the several views, there is showna brush holder 10 of general rectangular configuration made of bronze orother material and being capable of supporting brushes in the usualmanner. The brush holder consists of a box 12 having generally flatsides, open at its top and bottom ends, and of a design permittingattachment to a yoke provided on the machine. A plurality of parallelchannels or passageways l4, l6, 1% and 2t? extend vertically along itslength for receiving a carbon brush 22 and spring assembly 24 designedto urge the brush into firm contact with a commutator 25.

Referring now to the box 12, the spaced channels 14, 16, 18 and 20 arepositioned in line with one another with the larger of the channels l6being utilized for receiving carbon brush 22. The channel 2% shown atthe extreme right of the box 12 is formed by the walls of the box and isequipped with an elongated slot 28 through which a bolt 3t? is adaptedto extend for attaching the box to a yoke 32 atiixed on a side of themachine. Channel 18 positioned adjacent thereto is formed by a pair ofoppositely disposed but inwardly directed flanges 34, the bottom of thechannel terminating in a stop member 36 for limiting the extent ofdownward movement of spring assembly 24 and thereby precludinginadvertent contact with the commutator.

As shown in Figure 3, a second pair of inwardly directed flanges it)coact with flanges 34 in forming the channel 16 which is of a size forreceiving the brushes 22. Wire shunts 38 extend from the brushes in theusual manner. The flanges 40 merge into a solid wall which serves as areaction surface for the brushes during machine operation, while theopposite flanges 34 extend substantially to the bottom of the box 12 andthe space between the latter flanges is employed for permittingunobstructed downward movement of constant pressure spring 44 as itfollows the brushes as trey wear from use in the machine. it has beenfound that the coasting effect between the reaction surface, brush andspring imparts excellent stability to the brush when in contact with therotating commutator.

The outermost channel 14 is provided with a smooth outer wall 45 havinga slot 46 bridged near the bottom with a horizontal bar 48 for a purposehereinafter described. The upper ends of the wall 45 on opposite sidesof slot 46 are bent over to engage the flanges 46 at 41.

The spring assembly shown in Figure 4 consists of a U-shaped member 5dhaving legs 52 and 54 which are respectively provided with an outwardlydirected projection 56 and lugs 53, and a spring 44 attached to an innerportion of leg 54, as by rivets 69. As indicated above, the spring 44 isof a constant pressure type capable of exerting a predetermined pressureon the brushes regardless of the size or state of wear thereby assuringfirm contact with the commutator during their useful life. The U-shapedmember is made of spring metal with the legs 52 and 54 being spaced adistance slightly greater than the position they assume when the springassembly is set in the brush holder.

In operation, after the box 12 has been rigidly attached to the yoke 32and the brushes 22 inserted therein, the legs 52 and 54 are pressedinwardly and respectively inserted in channels 14 and 18 provided in thebox. By pressing downwardly on the U-shaped member 50, the spring 44 iscaused to unwind as it contacts the top of the brushes 22.Simultaneously, the legs 52 and 54 frictionally engage the walls oftheir respective channels and when the assembly assumes its finalposition, leg 54 is held in the channel only by friction of the legagainst the inner wall surface. Leg 52 on the other hand, moves againstthe inner surface of wall 45 until projection 56' slides over thehorizontal bar 48 and subsequently snaps outwardly thereby locking thespring assembly in position when downward pressure thereon is removedand the projection 56 permitted to lock itself on the horizontal bar 48.It will be evident that at this time, the upper ends of wall 45 are bentover to contact flanges 40 at 41.

When removal or replacement of the brushes is necessary, downwardpressure need only be exerted on the top of U-shaped member 59 by onehand of an operator, such pressure being efiective to move theprojection 56 out of contact with bar 48. With the parts in thisposition, removal of the pressure permits the constant pressure spring44 to move the spring assembly in an upward direction and out of the box12. Since the top ends of side 45 have been turned over against theflanges 40' at 41, the lugs 58 on leg 52 will hang up at this pointthereby maintaining the spring assembly captive on the brush holder.

Reflection on the structure described above will show that only threeparts are incorporated in this improved brush holder, namely, theU-shaped member 50, spring 44 and box 12, whereas a multitude of partsare required in prior structures. Further, the process of brush removalis simplified to a single step wherein only a single downward movementof the spring assembly is necessary to effect disengagement from theoperative position, and the assembly remains captive on the holderduring the brush removal and replacement operation.

Obviously, many modifications and variations are possible in light ofthe above teachings. It therefore is to be understood that within thescope of the appended claims, the invention may be practiced otherwisethan as specifically described.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A brush holder for use with a dynamoelectric machine comprising a boxof generally rectangular configuration having sides and open ends, aspring assembly, a plurality of channels formed by partitions in saidbox for respectively receiving a carbon brush and the legs of saidspring assembly utilized in urging the brush into firm contact with acommutator, a coiled spring attached to one of said legs and a cut outportion in one of said walls of a size sulficient to permit said springto extend therethrough and thereby follow the brush as it wears duringuse, a stop in one of said channels for preventing said spring assemblyfrom accidentally contacting said commutator, retaining means in theother of said channels arranged for coaction with said spring assemblyfor bolding the latter in said box against the action of said spring,and captive means on said box eitective in retaining said springassembly on said box when moved to an inoperative position.

2. A brush holder for use with a dynamoelectric machine comprising a boxof generally rectangular configuration having a channel for receiving acarbon brush, a narrow channel on each side of the brush channel, aspring assembly comprising a U-shaped member having a projection on oneend and a constant pressure spring attached to its other end, the endsof said U-shaped memher being of a size to permit reception by saidnarrow channels and arranged in a manner whereby said spring overliessaid brush, a bridging member in a wall of said box adjacent one of saidchannels positioned for coaction with said projection for locking saidspring assembly in said holder against the action of said spring, andcaptive means on said box arranged for engagement by said springassembly for retaining the latter thereon when moved to an inoperativeposition.

3. A brush holder for use with a dynamoelectric machine comprising a boxhaving a first channel for receiving a carbon brush, second and thirdchannels on opposite sides of said first channel designed forrespectively accepting spaced legs of a U-shaped spring assembly, acoiled spring mounted on one of said legs, stop means in said secondchannel limiting the lowermost position of one of said legs, and an openarea in a wall separating said first and second channels therebypermitting said coiled spring to move downwardly on a brush as thelatter wears from use, said third channel having stop means provided ina wall thereof adapted for engagement by a coacting projection on theother of said legs efiective in locking said spring assembly in saidbox, and captive means on said box for retaining said spring assemblywhen moved to an unlocked position.

References Cited in the file of this patent UNITED STATES PATENTS747,696 Geisenhoner Dec. 22, 1903 862,951 Waters Aug. 13, 1907 2,280,735Weissinger Apr. 21, 1942

